The encounter took place at the Rongfung forest area in Karbi Anglong district bordering Meghalaya on Thursday evening. Nityananda Goswami, aged 58 and the SP of Hamren police district falling under Karbi Anglong, was missing along with his personal security guard Ratul Nunisa ever since the gunfight of Thursday. Their bodies were retrieved on Friday morning.

Goswami had joined as SP in the police district in February 2012. He is survived by his wife and son, who studies in New Delhi.

The incident comes within months of the killing of an additional SP by the militants in Sonitpur district of the state.

Goswami was leading an 18-member search party of the police when the encounter took place. He was accompanied by an additional SP and the officer-in-charge of a police station among others. The personnel had split into three groups during the search.

"They had gone there to conduct a search operation following receipt of specific information about the movement of militants," Assam's director general of police Khagen Sarma, who visited the district on Friday, told dna.

He said three militant outfits including the Karbi People's Liberation Tigers (KPLT) and United People's Liberation Army (UPLA) were active in the area and as such, only an enquiry could reveal which group was involved.

The KPLT is a breakaway faction of the Karbi Longri NC Hills Liberation Front.

Formed in 2010, the outfit demands the creation of a Hemprek Kanthim (self-ruled state) for tribal Karbis.

"It is a setback for us. But the sacrifice made by him (Goswami) will not go in vain. We will step up our operations against the insurgents," Sarma warned.

The ministry of home affairs has expressed concern over the incident. "We have sought a report from the state government," Union minister of state for home Kiren Rijiju said.

Assam chief minister Tarun Gogoi has condemned the incident. He reviewed the prevailing law and order in the state during an emergency meeting.